1. Field of the Invention
The present invention relates to an apparatus controlling an operation of a motor and control method thereof enabling to operate the motor in accordance with a phase resistance value varying by a temperature increase of the motor in a washing machine.
2. Description of the Background Art
Generally, a washing machine using a sensorless BLDC(brushless direct current) motor detects a phase current and a phase voltage applied to the motor built inside so as to actuate the motor.
FIG. 1 illustrates a constructional block diagram of a general apparatus for controlling an operation of a sensorless BLDC motor.
Referring to FIG. 1, a general apparatus for controlling an operation of a sensorless BLDC motor includes a comparator 1 outputting a comparison signal by comparing a user-demanding command speed(speed signal) Wr of a motor 5 to a presumptive speed of the motor 5, a speed controller 2 outputting a speed control signal by receiving the comparison signal from the comparator 1, a current/voltage command generator 3 generating current and voltage commands by receiving the speed control signal outputted from the speed controller 2 and a position signal of a rotor of the motor 5, an inverter unit 4 converting a DC voltage generated by the voltage command into a three-phases AC voltage and outputting the converted AC voltage to the motor 5, a current/voltage detector 6 outputting a current/voltage detect signal by detecting phase voltage and current values of the three phases applied to the motor 5, and a speed/position calculation unit 7 outputting a position signal by calculating a rotor position inside the motor 5 by detecting the phase voltage and current values and outputting a speed signal by calculating a real-time speed of the motor.
Operation of the general apparatus for controlling an operation of the sensorless BLDC motor is explained as follows.
First, the comparator 1 compares the user-demanding speed (speed signal) of the motor to the presumptive speed signal of the motor and then outputs the corresponding comparison signal.
The speed controller 2 receives the comparison signal from the comparator 1 so as to output the speed control signal. Namely, the speed controller 2 based on the comparison signal outputs the speed control signal increasing the speed of the motor 5 if the calculated speed of the motor 5 is slower than the user-demanding speed of the motor 5, and the other speed control signal decreasing the speed of the motor 5 if the calculated speed of the motor 5 is faster than the user-demanding speed of the motor 5.
Thereafter, the current/voltage command generator 3 receives the speed control signal from the speed controller 2 and the position signal of the rotor inside the motor 5 from the speed/position calculation unit 7 so as to generate the current and voltage commands. The current/voltage command generator 3 then applies the current and voltage commands to the respective switching devices in the inverter unit 4. In this case, the inverter unit 4 converts the DC voltage generated by the voltage command into the three-phase AC voltage and then outputs the converted three-phase AC voltage to the motor 5. In this case, the motor 5 is driven by the three-phase AC voltage generated from the inverter unit 4.
Meanwhile, the current/voltage detector 6 detects the phase voltage and current values of the three phases applied to the motor 5 so as to output the current/voltage detect signal to the speed/position calculation unit 7.
Subsequently, the speed/position calculation unit 7 receives the phase voltage value and the phase current value from the current/voltage detector 6, calculates the received phase voltage and current values to calculate the position of the rotor in the motor 5, calculates the corresponding position signal and real speed of the motor 5, and outputs the corresponding speed signal to the current/voltage command generator 3 and the comparator 1, respectively. In this case, the speed/position calculation unit 7 calculates the speed of the motor 5 and the position of the rotor in the motor 5 using Formula 1.
Formula 1
KEwrsin xcex8r=Vaxe2x88x92Riaxe2x88x92Lsdia/dt 
KEwrsin (xcex8r+120)=Vbxe2x88x92Ribxe2x88x92Lsdib/dt 
KEwrsin (xcex8r+240)=Vcxe2x88x92Ricxe2x88x92Lsdic/dt 
In this case, R is a resistance, xcex8r is a rotor position in a motor, Ls is an inductance, Wr is a speed of the motor, Va, Vb, and Vc are phase voltages applied to the motor, ia, ib, and ic, are phase currents applied to the motor, and KE is a counter electromotive force.
Unfortunately, the general apparatus for controlling an operation of the sensorless BLDC motor fails to avoid varying the phase resistance value of the motor due to the temperature increase of the motor operated for a long time, thereby being unable to precisely control an operation of the motor and reducing a driving force of the motor.
Accordingly, the present invention is directed to an apparatus controlling an operation of a motor and control method thereof that substantially obviates one or more problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide an apparatus controlling an operation of a motor and control method thereof enabling to operate the motor stably and precisely by compensating the variation of a phase resistance value of the motor due to the temperature increase of the operator which is being operated.
Another object of the present invention is to provide an apparatus controlling an operation of a motor and control method thereof enabling to prevent the driving force of the motor from being decreased due to the temperature increase of the operator which is being operated.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a method of controlling an operation of a motor according to the present invention includes the steps of detecting a phase voltage value and a phase current value applied to the motor between forward and backward revolution sections of the motor, calculating a phase resistance value based on the detected phase voltage and current values, and controlling the operation of the motor by controlling a voltage applied to the motor in accordance with the calculated phase resistance value.
In another aspect of the present invention, an apparatus for controlling an operation of a motor includes a revolution section detect unit calculating an operational frequency of the motor based on phase voltage and current values applied to the motor and outputting a section detect signal by detecting an operational section of the motor in accordance with the calculated operational frequency, a calculation unit receiving the phase voltage and current values in accordance with the section detect signal so as to calculate a phase resistance value, a speed/position calculation unit calculating a rotor position of the motor by detecting the calculated phase resistance value and the phase voltage and current values and calculating a speed of the motor, and a voltage command generator generating a voltage command to apply a voltage to the motor based on the rotor position and the speed of the motor.
It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.